- Interestingly, recent reports demonstrated that EGCG has potent anti-COMT activity. These reports have shown that green tea extract intake is associated with weight loss due to diet-induced thermo-genesis. This effect is generally attributed to EGCG. This catechin is known to be capable of inhibiting COMT, which is the enzyme that degrades nor-epinephrine, thus stimulating thermo-genesis. The inhibition of COMT by EGCG was uncompetitive with respect to S-adenosylmethionine (SAM) suggesting that there is no direct interaction between EGCG and the SAM-binding site on the COMT, yet there was clear inhibition of COMT activity with increasing EGCG concentration. Additionally, the Vmax values for methylation were decreased. Our preliminary data also showed that EGCG inhibited COMT gene expression in a dose-dependent manner in human leiomyomata cells.